Segment Information (Tables)

6 Months Ended

Mar. 31, 2015

Segment Reporting [Abstract]

Schedule of Segment Information

Financial information by business segment follows:

Three Months Ended March 31, 2015:

			Reportable Segments
	Total		Gas Utility		Electric Utility		Other
Revenues	$	500,573	$	468,000	$	32,323	$	250
Cost of sales	$	278,336	$	258,155	$	20,181	$	—
Depreciation and amortization	$	15,644	$	14,489	$	1,155	$	—
Operating income (loss)	$	142,699	$	139,303	$	3,510	$	(114	)
Interest expense	$	10,611	$	10,104	$	507	$	—
Income (loss) before income taxes	$	132,088	$	129,199	$	3,003	$	(114	)
Capital expenditures	$	41,280	$	39,202	$	2,078	$	—

Three Months Ended March 31, 2014:

			Reportable Segments
	Total		Gas Utility		Electric Utility		Other
Revenues	$	513,956	$	480,163	$	33,552	$	241
Cost of sales	$	300,424	$	278,748	$	21,676	$	—
Depreciation and amortization	$	14,643	$	13,575	$	1,068	$	—
Operating income (loss)	$	137,954	$	134,560	$	3,492	$	(98	)
Interest expense	$	8,806	$	8,362	$	444	$	—
Income (loss) before income taxes	$	129,148	$	126,198	$	3,048	$	(98	)
Capital expenditures	$	31,648	$	30,039	$	1,609	$	—

Six Months Ended March 31, 2015:

			Reportable Segments
	Total		Gas Utility		Electric Utility		Other
Revenues	$	787,879	$	728,478	$	58,746	$	655
Cost of sales	$	421,388	$	385,363	$	36,025	$	—
Depreciation and amortization	$	31,069	$	28,769	$	2,300	$	—
Operating income (loss)	$	218,339	$	211,149	$	7,229	$	(39	)
Interest expense	$	21,260	$	20,234	$	1,026	$	—
Income (loss) before income taxes	$	197,079	$	190,915	$	6,203	$	(39	)
Capital expenditures	$	96,309	$	92,694	$	3,615	$	—
As of March 31, 2015
Total assets (at period end)	$	2,506,043	$	2,359,060	$	146,983	$	—
Goodwill (at period end)	$	182,145	$	182,145	$	—	$	—

Six Months Ended March 31, 2014:

			Reportable Segments
	Total		Gas Utility		Electric Utility		Other
Revenues	$	812,855	$	751,725	$	60,513	$	617
Cost of sales	$	452,289	$	414,235	$	38,054	$	—
Depreciation and amortization	$	29,093	$	26,959	$	2,134	$	—
Operating income	$	223,797	$	216,613	$	7,181	$	3
Interest expense	$	17,603	$	16,748	$	855	$	—
Income before income taxes	$	206,194	$	199,865	$	6,326	$	3
Capital expenditures	$	65,902	$	62,851	$	3,051	$	—
As of March 31, 2014
Total assets (at period end)	$	2,340,617	$	2,195,437	$	145,180	$	—
Goodwill (at period end)	$	182,145	$	182,145	$	—	$	—